1. Field of the Invention
The present invention relates to apparatus and methods for driving a plasma display panel (PDP).
2. Description of the Related Art
In recent years, flat panel displays such as liquid crystal displays (LCDs), field emission displays (FEDs), PDPs, and the like have been actively developed. PDPs are advantageous over other flat panel displays by providing high luminance, high luminous efficiency and wide view angles. Accordingly, PDPs are favorable as substitutes for conventional cathode ray tubes (CRT) for making large-scale screens of 40 inches or more.
A PDP is a flat panel display, that uses plasma generated by gas discharge, to display characters or images, and it includes, according to its size, more than several scores to millions of pixels arranged in a matrix pattern. Such a PDP is classified as a direct current (DC) type or an alternating current (AC) type according to the PDP's discharge cell structure and the waveform of the driving voltage applied thereto.
DC PDPs have electrodes exposed to a discharge space, allowing a direct current to flow through the discharge space while voltage is applied. Thus, for DC PDPs, resistors are used to limit the current. In contrast, AC PDPs have electrodes covered with a dielectric layer that naturally forms a capacitance component that limits the current and protects the electrodes from the impact of ions during a discharge. Thus, AC PDPs have longer lifetimes.
Typically, a driving method of AC PDPs is sequentially composed of a reset step, an addressing step, a sustain discharge step, and an erase step.
In the reset step, the state of each cell is initialized in order to readily perform an addressing operation on the cell. In the addressing step, wall charges are accumulated on selected “on”-state cells and other “on”-state cells (i.e., addressed cells) for selecting “off”-state cells on the panel. In the sustain discharge step, a sustain pulse is applied alternately to scan electrodes (hereinafter referred to as “Y electrodes”) and sustain electrodes (hereinafter, referred to as “X electrodes”) to perform a discharge for displaying an image on addressed cells.
In AC PDPs, the Y and X electrodes for such a sustain discharge act as a capacitive load, and a capacitance exists for the Y and X electrodes (hereinafter referred to as a “panel capacitor Cp”).
Now, a description will be given as to a driver circuit for a conventional AC type PDP and its driving method.
FIG. 1 illustrates a conventional driver circuit and FIG. 2 illustrates an operating waveform of the conventional driver circuit illustrated in FIG. 1.
The driver circuit generating a sustain pulse, as suggested by Kishi et al. (Japanese Patent No. 3201603), comprises, as shown in FIG. 1, a Y electrode driver 11, an X electrode driver 12, a Y electrode power supplier 13, and an X electrode power supplier 14. The X electrode driver 12 and the X electrode power supplier 14 are the same in construction as the Y electrode driver 11 and the Y electrode power supplier 13, and will not be described in detail in the following description.
The Y electrode power supplier 13 comprises a capacitor C1, and three switches SW1, SW2, and SW3. The Y electrode driver 11 comprises two switches SW4 and SW5. The switches SW1 and SW2 in the Y electrode power supplier 13 are coupled in series between a power source Vs and a ground voltage GND. One terminal of the capacitor C1 is coupled to the contact of the switches SW1 and SW2, and the switch SW3 is coupled between the other terminal of the capacitor C1 and the ground voltage GND.
The switches SW4 and SW5 of the Y electrode driver 11 are coupled in series to both terminals of the capacitor C1 of the Y electrode power supplier 13. The contact of the switches SW4 and SW5 is coupled to the panel capacitor Cp.
As shown in FIG. 2, when the switches SW4 and SW4′ are turned on, with the switches SW1, SW3, and SW2, on and the switches SW2, and SW5 off, the Y electrode voltage Vy is increased to Vs and the capacitor C1 is charged with the voltage Vs.
Subsequently, when the switch SW5 is turned on, with the switch SW4 off, the Y electrode voltage Vy is decreased to the ground voltage. When the switches SW1, SW3, and SW4 are turned off and the switches SW2 and SW5 are turned on, the Y electrode voltage Vy is decreased to −Vs by the voltage Vs charged in the capacitor C1. When the switch SW5 is off and the switch SW4 is on, the Y electrode voltage Vy is increased to the ground voltage 0V.
Through this driving operation, positive voltage +Vs and negative voltage −Vs can be alternately applied to the Y electrodes. Likewise, positive voltage +Vs and negative voltage −Vs can be alternately applied to the X electrodes. The voltages ±Vs respectively applied to the X and Y electrodes have an inverted phase with respect to each other. By generating a sustain pulse swinging between −Vx and +Vs, the potential difference between X and Y electrodes can be maintained at the sustain discharge voltage 2Vs.
Such a driver circuit can employ elements of a low withstand voltage, because the withstand voltage of each element in the circuit is Vs. However, this driver circuit is applicable only to plasma display panels using a pulse swinging between −Vs and +Vs.
In addition, the capacitor for storing the voltage used as a negative (−) voltage in this circuit must have a large capacity, so a considerable amount of an inrush current flows in an initial starting step due to the capacitor.